Texture duplicated on opposite side of object
It seems like you've unwrapped the object with one of the "project from view" options. This means your UV map is just a flattened version of your mesh; the faces on the far side overlap the faces on the near side, and so end up bearing a reversed version of whatever image you position there.

A simple workaround is to select the faces you don't want to texture, then (in the UV editor) scale their UV mapping to 0 (S0) and tuck them away in the corner somewhere.